1. Field of the Invention
This invention relates to the stabilization with respect to electromagnetic radiation of organic compounds, particularly to the stabilization of dyes used in photographic applications, especially those used in photographic elements.
2. Description of the Prior Art
A need has been long recognized in the photographic arts for imaging dyes which are more resistant to fading upon extended exposure to electromagnetic radiation, such as ambient light. It is common practice to form color photographic images using combinations of dyes which form subtractive primary colors. Such subtractive primary dyes are those which absorb light predominantly in one of the blue, green and red triads of the visible spectrum thereby appearing yellow, magenta or cyan, respectively. In the most common arrangement these subtractive primary dyes lie in separate layers of the photographic element. In such photographic elements the magenta dyes have shown a particular propensity toward fading upon prolonged exposure to light.
It is known that organic dyes, such as indophenol, indoaniline, azo and azomethine dyes can be given some measure of protection against visible and ultrviolet radiation by mixing with various compounds, especially phenolic type compounds having fused heterocyclic ring systems.
It is also known to incorporate into a silver halide emulsion a mixture of colored and uncolored couplers which produce dye images of the same hue on coupling. See, for example, U.S. Pat. No. 2,428,054. This is done for purposes of masking undesired color in photographic negatives and not for purposes of imparting dye stability.
The improvement of the stability of organic substrate compounds to visible and ultraviolet light by the use of azomethine quenching compounds bathochromic to said substrate compounds is described in United States Patent Application Ser. No. 546,659 filed Feb. 3, 1975 of Smith et al. The ability of such azomethine compounds to quench singlet oxygen is also known.
Certain of the metal chelates employed in the practice of the present invention have been described by Schrauzer in Accounts of Chemical Research, Vol. 2, pp. 72 ff., March, 1969.
The use of Ni(II) chelates in the UV stabilization of polyolefins has been described by Cicchetti in Advances in Polymer Science, Vol. 7, pp. 70-112 (1970). It is pointed out in this article that the following patents relate to such stabilization: British 858,889; British 945,050; U.S. Pat. Nos. 3,296,191; 3,296,192; 2,971,941; British 943,061 and U.S. 3,310,575.
The use of certain metal (II) chelates to quench singlet oxygen in the liquid phase has been reported by Carlsson et al. in the Journal of the American Chemical Society/94:25/ Dec. 13, 1972 at pp. 8960 ff.
Bloom U.S. Pat. Nos. 3,588,216 and 3,806,462, issued June 28, 1971 and Apr. 23, 1974, disclose the use of chelated metal compounds for infrared filtering in optical elements, such as sun glasses.